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I'm getting stuttering along with hunting A/F values (as seen from the gauge) at part-throttle. Felt like a bad wideband sensor so I replaced with a Bosh LSU 4.9 sensor and nothing changed. I created a short data-log but don't have anyone locally who is familiar with Ktuner. Any recommendations on who could take a look and help diagnose?

If you're referring to the primary O2 that's compatible with these ECUs, it's a Denso and should be an OEM spec sensor. The ECU works in closed loop based on this sensor. If you replaced your external sensor for monitoring, that wouldn't help the ECU if it's a bad sensor.

Beyond that, sounds like it needs tuning.